A former Marine charged with murdering four people in Oklahoma City including an adult reality TV star has pleaded guilty, according to an assistant district attorney.A judge sentenced David Tyner to six consecutive life sentences without the possibility of parole Friday. Prosecutors say Tyner killed a man and three women in a southwest Oklahoma City home in 2009 and then set fire to the home.One of the women killed was Brooke Phillips, who starred on the HBO show "Cathouse," which has brought national attention to the case. Tyner was charged with six counts of murder due to the fact that two of the women killed were pregnant. Defense attorneys have argued that the case is purely circumstantial because no one saw Tyner shoot anyone or set the fire.